JPH05317892A - Method for removing salts from soil containing salts - Google Patents

Abstract

PURPOSE:To remove salts from soil, especially from sludge with a high water absorbency polymer and to reutilize the soil and the polymer. CONSTITUTION:A high water absorbency polymer 5 in a water absorbed state is brought into contact with water and salts-contg. soil 3. Concn. gradient of the salts is formed between the polymer 5 and the soil 3, only ions of the salts in the soil 3 are diffused and transferred into the polymer 5 and then the polymer 5 is brought into contact with water 11 to diffuse and transfer the salts into the water 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing salt-containing soil, and more particularly to a salt-containing soil from which salt in the salt-containing soil can be removed to obtain a plant-cultivable soil. Of salt removal method.

[0002]

2. Description of the Related Art Conventionally, as a method of desalinating seawater or underground irrigation, a pair of electrode plates are installed in an electrolytic cell, and cation exchange membranes and anion exchange membranes are alternately arranged between these electrode plates to carry out this electrolysis. Electricity was supplied while flowing water in the tank to remove salt. Thereby, concentration and desalting of irrigation water are simultaneously performed between the exchange membranes. However, since this method removes salts contained in the liquid of seawater or underground irrigation, it was impossible to desalt salt-containing soil such as sea sand and sludge. That is, in the method using the ion exchange membrane,
Since the exchange membrane is a thin membrane, it has drawbacks such as being easily broken when the earth and sand are put in, or by the pressure of the earth and sand, and being expensive. For this reason, as a method of removing salt from the earth and sand, generally, the earth and sand are washed with a large amount of water to remove salts.

[0003]

However, this method is not a rational method because a large amount of water is required to completely remove salts and it takes a considerable amount of time. In addition, since salt-containing soil such as sludge had very small particles, it was impossible to separate water from the soil, and it was impossible to remove salt. The present invention is to solve such problems, in particular, salt-containing soil such as sludge is desalted with a superabsorbent polymer, and a salt-containing soil that enables reuse of the soil and the superabsorbent polymer. It is an object to provide a method for removing salt from soil.

[0004]

Means for Solving the Problems That is, a method for removing salt from a salt-containing soil of the present invention is to bring a salt-containing soil containing a superabsorbent polymer into contact with the salt and ionize the salt present in the soil with water. After removing the salt by absorbing it together, the superabsorbent polymer is further brought into contact with water to diffuse and migrate salts into water,
It is said that the super absorbent polymer can be reused. Also,
In the present invention, a salt concentration gradient is provided between the superabsorbent polymer and the soil by contacting the salt-containing soil containing the superabsorbent polymer in the water absorbing state, and only the salt ions in the soil are superabsorbent. It also includes a method of desalting salt-containing soil that diffuses and migrates into polymers.

In the concrete method of removing salt-containing soil according to the present invention, as in the salt-removing apparatus 1 shown in FIG. The dried superabsorbent polymer 5 is placed through the material 4. As a result, water, Na ions, and Cl ions are absorbed by the superabsorbent polymer 5 from the salt-containing soil 3 through the water permeable material 4. The superabsorbent polymer 5 releases water to the outside of the system by solar heat and maintains a certain absorbing ability. Further, water is supplied to the salt-containing soil 3 so as not to disconnect the water layer in the soil, that is, the water channel provided between particles of sand or the like.

On the other hand, in the salt removing apparatus 7 shown in FIG.
3 areas 8, 9 and 10 are provided by a water permeable material 4, the superabsorbent polymer 5 which has absorbed water is put into the central area 9, and the other areas 8 and 10 respectively contain water containing salt 3 And add water 11. This water 11 can flow continuously, and may be water drawn from the river 12, for example. As a result, soil 3, super absorbent polymer 5
Then, a concentration gradient of NaCl is generated between the water 11, and Na ions and Cl ions in the salt-containing soil 3 are constantly diffused and transferred from the water-permeable material 4 to the superabsorbent polymer 5 and then to the water 11. Continues until the NaCl concentration gradient disappears. N
When the aCl concentration gradient disappears and the desalination of the salt-containing soil 3 is completed, the soil 3 and the water 11 are discharged, and then the soil 3 again.
And add water 11. It should be noted that the water 11 does not easily flow back into the soil 3 because of the presence of the superabsorbent polymer 5. The water-permeable material 4 is not particularly limited as long as it allows water to pass through and has strength. For example, a woven fabric or a non-woven fabric is most suitable.

The superabsorbent polymer used in the present invention is a gel having a hydrophilic group such as a carboxyl group, an amino group or an ether group in the main chain or side chain of the molecule and partially crosslinked. Yes, specifically, there are polyacrylic acid, polyacrylic acid salt, polyvinyl alcohol, polyacrylamide, polyether polyurethane and the like. The superabsorbent polymer may be in the form of powder, lumps, plates, or a shape surrounded by a water-permeable material such as paper or cloth.

The amount of the super absorbent polymer used is determined by the amount of soil, the water content, the salt concentration, and the method of contacting the super absorbent polymer with the soil. For example, a normal superabsorbent polymer can absorb several 100% of a 5% aqueous solution of NaCl with respect to the weight of the polymer, so that the water content of the soil is several 1%.
It is sufficient to use 1/00. However, in reality, it is difficult to exert 100% of the water-absorbing ability of the superabsorbent polymer depending on the particle size and water content of the soil and the manner of contact between the superabsorbent polymer and the soil. Therefore, the amount of superabsorbent polymer used is determined depending on the condition of the soil and the contacting method between the soil and the superabsorbent polymer.

The soil used in the present invention is not particularly limited. However, in the present invention, the water layer in the soil must be a continuous layer in order to transfer water and salt ions. The salt removal method of the present invention does not work on salt-containing soil containing no water unless water is added.

As a method for bringing the above-mentioned soil into contact with the superabsorbent polymer, there is a method of mixing and burying the superabsorbent polymer in the soil in addition to the salt removing apparatus 1 described above. Further, the superabsorbent polymer can be placed in the lower layer, upper layer, or side layer of the soil. In particular, when a powdery or lumpy superabsorbent polymer is mixed in the soil, the contact area between the soil and the superabsorbent polymer increases, and as a result, salt removal efficiency increases.

[0011]

EFFECTS OF THE INVENTION According to the present invention, a salt-containing soil containing a superabsorbent polymer is brought into contact with the salt to ionize salts present in the soil together with water, or the superabsorbent polymer in a water absorbing state. By contacting with salt-containing soil containing water, a salt concentration gradient is established between the superabsorbent polymer and the soil. After absorbing or diffusing and transferring only the water-absorbing polymer to the superabsorbent polymer, the superabsorbent polymer is brought into contact with water to diffuse and transfer salts into the water to remove sludge that could not be washed. The superabsorbent polymer used for salt removal can be used again for salt removal by washing with water.

[0012]

Next, the present invention will be described in more detail with reference to specific examples. Example 1 1 part by weight of polyacrylate (PAA: Aqua Reserve AP-100 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) dried in an aqueous solution of 5% and 15% NaCl was added to 100 parts by weight of the aqueous solution. Ether urethane (PEU: manufactured by Takiron Co., Ltd.) was also immersed in 5 parts by weight in the same aqueous solution. After a predetermined time, the aqueous NaCl solution was sampled, and Na and Cl were quantitatively analyzed by fluorescent X-ray analysis to determine the concentration in the aqueous solution. The result is shown in FIG.

The superabsorbent polymer absorbed the aqueous solution immediately after the immersion, and after 24 hours in the 5% NaCl aqueous solution, showed a weight increase of about 100 times for PAA and about 10 times for PEU. On the other hand, in the case of a 15% NaCl aqueous solution, it is about 10 with PPA.
That is, the weight increase of PEU was about 5 times. At this time, since the Na and Cl concentrations in the aqueous solution hardly change,
PPA and PEU show that they also absorb Na and Cl ions in aqueous solution with water. However, the absorption of the NaCl aqueous solution seems to differ depending on the type of superabsorbent polymer.
The a concentration tends to increase, and it is difficult to absorb Na. On the other hand, PE
In the case of U, the Na and Cl concentrations of the aqueous solution tend to decrease,
It absorbs Na and Cl better than water.

Example 2 70 parts by weight of calcium carbonate (particle size 1 μm) was added to Na.
30 parts by weight of a 15% Cl aqueous solution was added and mixed, and then dried polyacrylic acid gel (PAA: Aqua Reserve AP-100 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was added to 100 parts by weight of the pseudo soil. The filter paper was contacted with 3 parts by weight for 48 hours. Then, the pseudo soil is 120
After drying at ° C for 24 hours and measuring the water content, 100 parts by weight of ion-exchanged water was mixed with 100 parts by weight of dry simulated soil, allowed to stand, and the supernatant liquid was sampled. Fluorescent X-ray analysis The amount of Na in the pseudo soil after the test was quantified by the device. The results are shown in Table 1.

Example 3 The same evaluation was performed by changing the polyacrylic acid gel of Example 2 to polyether polyurethane (PEU: manufactured by Takiron Co., Ltd.). The results are shown in Table 1.

Example 4 The same evaluation was performed by changing the polyacrylic acid gel of Example 2 to polyvinyl alcohol gel (PVA: GP01 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.). The results are shown in Table 1.

Comparative Example 1 The same evaluation was carried out with the pseudo soil alone without using the polyacrylic acid gel of Example 2. The results are shown in Table 1.

[0018]

[Table 1]

From the above results, by contacting the dried superabsorbent polymer with the soil containing the salt, the superabsorbent polymer absorbs the salt in the soil together with water to remove the salt from the soil. You can see that

Example 5 Polyacrylic acid salt (PAA: Aqua Reserve AP-100 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was charged with ion-exchanged water and PA.
1/50 and 1/250 by weight ratio of A / ion-exchanged water
Absorbed by. These wet samples and 5% and 15% aqueous NaCl solutions were wet sample / NaCl aqueous solution = 1: 1.
In the same manner as in Example 1, changes in the Na and Cl concentrations of the aqueous NaCl solution were examined. The result is shown in FIG. When the wet sample was immersed in the aqueous NaCl solution, the Na and Cl concentrations of the aqueous NaCl solution were immediately reduced to about 1/2, and it was found that Na and Cl ions of the aqueous NaCl solution were transferred to the wet sample. This is because Na and Cl ions were diffused and transferred from the aqueous solution to the wet sample according to the concentration gradient formed between the NaCl aqueous solution and the wet sample.

Example 6 Na for 70 parts by weight of calcium carbonate (particle size 1 μm)
A polyacrylic acid salt (PAA: Aqua Reserve AP-100 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) in which 5000 wt% of ion-exchanged water was absorbed into the pseudo soil obtained by adding 30 parts by weight of Cl 15% aqueous solution and mixing. The filter paper was contacted with 30 parts by weight for 48 hours. After that, 12 pseudo soils
After drying at 0 ° C for 24 hours and measuring the water content, 100 parts by weight of ion-exchanged water was mixed with 100 parts by weight of the dry simulated soil, allowed to stand, and the supernatant liquid was sampled. The amount of Na in the pseudo soil after the test was quantified by the analyzer. The results are shown in Table 2.

Example 7 As in Example 6, the soil in which the salt concentration was lowered was contacted with a polyacrylic acid salt in which 5000 wt% of ion-exchanged water had been absorbed for 24 hours, and the same operation was repeated 3 times. I repeated. The amount of Na in the soil after the test was quantified. The results are shown in Table 2.

Example 8 The amount of Na in the soil after the test was quantified in the same manner as in Example 6 except that the amount of polyacrylate used was 150 parts by weight. The results are shown in Table 2.

Comparative Example 2 The amount of Na in the initial soil was quantified without using the polyacrylic acid gel of Example 6. The results are shown in Table 2.

[0025]

[Table 2]

From the above results, a salt concentration gradient was established between the soil and the superabsorbent polymer by bringing the superabsorbent polymer, which absorbed a large amount of water, into contact with the soil containing the salt, and A part could be diffused and transferred into the superabsorbent polymer. In addition, this result shows that the salt in the superabsorbent polymer diffuses into water by bringing the salt-absorbing polymer into contact with water to establish a salt concentration gradient between the superabsorbent polymer and water. , It is also shown to be migrated. Therefore, the super absorbent polymer used for salt removal is not disposable,
It can be used again.

[0027]

INDUSTRIAL APPLICABILITY As described above, in the present invention, the salt-containing soil containing the superabsorbent polymer is brought into contact with the salt to ionize the salt present in the soil together with water, or to absorb water. By contacting a salt-containing soil containing a certain superabsorbent polymer, a salt concentration gradient is established between the superabsorbent polymer and the soil, so that the salts that are ionized in the soil are superabsorbent. After diffusion and transfer to the polymer, the superabsorbent polymer is brought into contact with water to diffuse and transfer salts into the water, whereby sludge which could not be washed can be removed. By washing the superabsorbent polymer used in the above with water, it can be used again for salt removal.

[Brief description of drawings]

FIG. 1 is a side view of a salt removing apparatus used in the salt removing method for salt-containing soil of the present invention.

FIG. 2 is a side view of another salt removing apparatus used in the salt removing method for salt-containing soil of the present invention.

FIG. 3 shows the N of the sample in Example 1 measured by X-ray fluorescence analysis.
It is a graph which shows the time change of a or Cl concentration.

FIG. 4 is an N by fluorescent X-ray analysis of the sample in Example 5.
It is a graph which shows the time change of a or Cl concentration.

[Explanation of symbols]

 1 salt removal device 2 container 3 salt-containing soil 4 water permeable material 5 super absorbent polymer 7 salt removal device 8 area 9 area 10 area 11 water 12 river

Front page continuation (72) Inventor Yoshio Yamaguchi 4-1-21, Hamazoe-dori, Nagata-ku, Kobe Mitsuboshi Belt Co., Ltd.

Claims (2)

[Claims] 1. A method of contacting a salt-containing soil containing a water-containing superabsorbent polymer, absorbing salts ionized in the soil together with water, and then contacting the superabsorbent polymer with water. A method for removing salt-containing soil, which comprises diffusing and transferring salts into water. 2. A salt concentration gradient is provided between the superabsorbent polymer and the soil by contacting the salt-containing soil containing the superabsorbent polymer in a water-absorbing state to increase only the salt ion in the soil. After being diffused and transferred into the water-absorbent polymer, the super-water-absorbent polymer is further brought into contact with water to diffuse salts into water,
A salt removal method for salt-containing soil, which comprises migrating.